1. Field of the Invention
The invention is directed to a medical instrument for phacoemulsification with which the biological tissue of a lens of the eye is comminuted by the introduction of energy, the comminuted product is sucked out through an incision in the cornea, while intraocular pressure is maintained by supplying an irrigating liquid.
2. Discussion of the Relevant Art
For purposes of carrying out the above-mentioned operation, the known prior-art instruments have a supply cannula for the irrigating liquid and a suction cannula for the core and core fragments. In conventional methods for phacoemulsification, a cannula is inserted into the eye to suck out the cataractous lens core in its entirety. However, this method, known since 1967, can be advantageously applied only for soft lenses.
With hard cores, the lens material is first comminuted by supplying energy, preferably via ultrasound or laser, and the small fragments are then sucked out through the suction cannula which is enclosed by a handpiece. The volume of liquid and lens fragments sucked out of the anterior chamber is compensated by an infusion of rinsing liquid into the anterior chamber via the supply cannula, so that intraocular pressure is substantially maintained.
The supply of liquid, known as irrigation, is carried out in all known handpieces via a supply cannula which is constructed as a sleeve that is fitted over the suction cannula. During the operation, the liquid flows between the suction cannula and the inner wall of the sleeve to the distal end of the handpiece, where two outlet openings are generally provided
The introduction of energy is currently carried out by ultrasound in more than 90% of cataract extractions. It is disadvantageous that the introduction of ultrasound into the tissue involves unwanted generation of heat, so that cooling must be carried out in order to prevent damage to healthy tissue. To this extent, the sleeve serves a dual function in ultrasound phacoemulsification in that the liquid flowing between the suction cannula and inner wall of the sleeve is utilized for cooling at the same time. For this reason, handpieces for phacoemulsification using ultrasound technology are, in principle, constructed only with integrated supply cannula, suction cannula and integrated ultrasound conductor.
Because of the need to supply liquid and the formation of the sleeve as a cooling element, the distal end of the handpiece is necessarily relatively large. Accordingly, the suction cannula, for example, which itself has a diameter in the range of 0.8 mm to 1.3 mm, is enlarged to a diameter of about 2.5 mm through the use of the sleeve which is drawn over it. In order to introduce a cannula with these dimensions into the tissue, an incision on the order of 3 mm to 3.2 mm is necessary.
However, large incisions of this kind result in loss of aqueous humor and rinsing solution during the operation. Further, the risk of astigmatism induced by the operation increases as the size of the incision increases. Visual rehabilitation also progresses relatively slowly with incisions of this size compared to smaller incisions.
For this reason, medical efforts are directed to increasingly smaller incisions with the purpose of introducing injectable lenses into the anterior chamber through these small incisions. However, it is necessary for this purpose that the comminuted lens material can be sucked out through small incisions and that irrigating liquid can be supplied through the same.
Further, laser phacoemulsification is known from the prior art in which energy is introduced via laser radiation which is aimed directly on the tissue to be comminuted. A laser wavelength with a very small depth of penetration into the aqueous matter in the interior of the eye must be selected; wavelengths in the low UV range and infrared range are suited to this purpose. In this connection, the use of Er:YAG lasers with a wavelength of xcex=2.9 xcexcm has proved successful. In this way, a quasi-nonthermal introduction of energy is achieved and the problems arising from the use of ultrasound with respect to heat generation no longer occur.
However, the handpieces known from the prior art for laser phacoemulsification likewise have the disadvantage that the supply cannula, suction cannula and energy supply (for example, via light-conducting fibers) are integrated in a handpiece and the outlets are spatially oriented to a common area. This also requires a large incision through which the supply of irrigating liquid and laser energy and the aspiration of comminuted core material must be carried out.
On this basis, it is the primary object of the invention to provide a medical instrument for phacoemulsification by which it is possible to replace the lens through small incisions in the cornea while maintaining the advantageous quasinonthermal introduction of energy.
According to the invention, this object is met in a medical instrument for phacoemulsification with which the biologcal tissue of a lens of the eye is ablated by the introduction of energy, the ablated product is sucked out through an incision in the cornea and the intraocular pressure is maintained by supplying an irrigating liquid. The instrument comprises two cannulas for sucking out the ablated lens material and for supplying the irrigating liquid. At least one device is provided for the introduction of energy through laser radiation. The two cannulas are enclosed by separate handpieces which are movable relative to one another. One of the handpieces with the first cannula communicates with a suction device via a feed line. The other of the handpieces with the second cannular communicates with a supply device for the irrigating liquid via another feed line.
With the medical instrument suggested according to the invention, it is possible to carry out phacoemulsification through small incisions resulting essentially in the advantages that the risk of inducing astigmatism is now only slight, a quicker postoperative visual rehabilitation is also possible and a lens can now be introduced into the eye through injection in an accessible phacoemulsification technique.
In this connection, a highly preferred application of the instrument suggested according to the invention consists in that after the comminuted core material is sucked out via one of the two handpieces or via the cannula integrated in the respective handpiece, the substance is injected, remains in the eye and replaces the old eye lens.
For this purpose, in constructional variants of the invention, the handpieces or the cannula are outfitted with connections for corresponding instruments for introducing a substance of this kind, e.g., for injection or the like.
In another preferred constructional variant, each of the two handpieces is provided for sucking out the comminuted core material and for supplying rinsing liquid. For example, when the cannulas of both handpieces are displaced with their distal end from opposite sides toward the lens of the eye, it is possible in this way to carry out the comminution of tissue as well as aspiration of the ablated products selectively and alternately in both of these opposite positions.
Compared with one-sided aspiration, this has the advantage that the cannula need not be introduced as deeply, which in turn fits in with the striving for small incisions and gentle treatment of tissue. For this purpose, both handpieces are connected, via transport lines or feed lines, to a switchable directional valve by means of which the flow directions can be reversed when sucking out the ablated product and when supplying the rinsing liquid. This switching can be carried out advantageously with a foot switch.
In this connection, it can further be provided that both handpieces are outfitted with fiber tips for supplying laser energy. The fiber tips can preferably be arranged inside the cannula and can also be arranged so as to be displaceable inside the cannula in the radiating direction of the laser energy and in the flow direction. This results in the advantage that the fiber tip can then be retracted from the treatment site, for example, when no laser energy is being radiated during irrigation. The outlet end of the respective cannula, in contrast to the fiber tip, remains directly at the treatment site.
In another very preferred construction of the invention, it is provided that a device for eliminating clogging within the cannula or within the feed lines is associated with one or both of the handpieces. This device can have, for example, a cleaning element which can be inserted laterally into the cannula and/or into one of the feed lines and which is displaceable within the respective line cross section. This cleaning element can be, for example, a flexible rod outfitted with a thickened end or a cleaning spiral whose diameters are adapted to the line cross section.
Another advantageous construction consists in that one or both of the handpieces is/are outfitted with auxiliary instruments for holding, gripping, turning, pushing, cutting, splitting, protecting and/or illuminating the tissue at the treatment site. These auxiliary elements are preferably interchangeable and can be connected with the respective handpiece, for example, via an attaching mechanism. In this connection, further constructions are possible in which the auxiliary instruments can be retracted into the handpiece via a displacing mechanism or are arranged so as to be displaceable on the outside of the handpiece, so that they can be moved into the appropriate use position, as needed, at any time.